1. Field of the Invention
The present invention relates to a method of fabricating an optical waveguide of which the top face or the bottom face of the core layer is not covered by the clad layer, and which is suitable for use as an optical integrated circuit.
2. Description of the Prior Art
As ever greater capacity and higher speed of information processing in optical communication systems and computers are required today, optical waveguides are attracting increasing note as media for the transmission of light.
A known method of fabricating an optical waveguide comprises, for instance, a step of preparing a first clad member having a concave groove in its surface; a step of covering the concave groove and the surroundings of the concave groove by forming a coat of a first liquid high molecular material over the first clad member; a step of forming, by thermally treating the coat of the first liquid high molecular material, a core member having in its surface a depressed part whose height is lower at the concave groove than in the surroundings of the concave groove and whose depth is equal to or greater than the thickness of the surroundings of the concave groove; a step of forming a coat of a second liquid high molecular material over the first clad member and core member; and a step of forming, by thermally treating the coat of the second liquid high molecular material, a second clad member (see Japanese Patent Laid-Open No. 2002-350661).
However, an optical waveguide having no clad layer on the surface of the core part cannot be fabricated by this method.
On the other hand, there are methods by which an optical waveguide whose core member is not covered by a clad member can be fabricated. By a known one among such optical waveguide fabrication methods, a film consisting of a photosensitive material is formed over a substrate, then an optical waveguide core pattern is formed on that film by exposure to light, stabilizing after that the photosensitive material or its derivative to form a pattern layer consisting of a core part and a clad part (see Japanese Patent Laid-Open No. 2003-14966).
However, what is fabricated by this method is an optical waveguide of which neither the top face nor the bottom face of the core layer is covered by a clad layer, but an optical waveguide of which only one face of the top face and the bottom face of the core layer is not covered by a clad layer cannot be fabricated thereby.